题解 | #树的子结构#

import java.util.*;
/**
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }

}
*/
public class Solution {
    public boolean HasSubtree(TreeNode root1,TreeNode root2) {
        if(root1 == null || root2 == null) return false;
        return Issame(root1, root2) || HasSubtree(root1.right, root2) || HasSubtree(root1.left, root2);
    }
    boolean Issame(TreeNode root1, TreeNode root2){
        if(root2 == null) return true; //注意这两步的顺序
        if(root1 == null) return false;
        if(root1.val != root2.val) return false;
        return Issame(root1.right, root2.right) && Issame(root1.left, root2.left);
    }
}